Methods for cyclically etching a metal layer for an interconnection structure for semiconductor applications

ABSTRACT

Embodiments of the present disclosure provide methods for etching a metal layer, such as a copper layer, to form an interconnection structure in semiconductor devices. In one example, a method of patterning a metal layer on a substrate includes supplying a first etching gas mixture comprising a hydro-carbon gas and a hydrogen containing gas into a processing chamber having a substrate disposed therein, the substrate having a metal layer disposed thereon, supplying a second gas mixture comprising the hydrogen containing gas to a surface of the etched metal layer disposed on the substrate, and supplying a third gas mixture comprising an inert gas into the processing chamber to sputter clean the surface of the etched metal layer.

BACKGROUND

1. Field

Embodiments of the present disclosure generally relate to methods ofpatterning a metal layer, and more particularly to methods of cyclicallypatterning a copper material utilized to form interconnection structuresin semiconductor applications.

2. Description of the Related Art

Integrated circuits have evolved into complex devices that can includemillions of transistors, capacitors and resistors on a single chip. Theevolution of chip designs continually requires faster circuitry andgreater circuit density. The demands for faster circuits with greatercircuit densities impose corresponding demands on the materials used tofabricate such integrated circuits. In particular, as the dimensions ofintegrated circuit components are reduced to the sub-50 nm scale, it isnecessary to use low resistivity conductive materials (e.g., copper) aswell as low dielectric constant insulating materials (dielectricconstant less than about 4) to obtain suitable electrical performancefrom such components.

The demands for greater integrated circuit densities also impose demandson the process sequences used in the manufacture of integrated circuitcomponents. As the physical dimensions of the structures used to formsemiconductor devices are pushed against technology limits, the processof accurate pattern transfer for structures that have small criticaldimensions and high aspect ratios has become increasingly difficult.Copper is commonly used to form interconnects a sub-micron device nodesdue to its low resistivity compared to aluminum. Copper interconnectsare electrically isolated from each other by an insulating material.When the distance between adjacent metal interconnects and/or thicknessof the insulating material has sub-micron dimensions, capacitivecoupling may potentially occur between such interconnects. Capacitivecoupling between adjacent metal interconnects may cause cross talkand/or resistance-capacitance (RC) delay which degrades the overallperformance of the integrated circuit. In order to prevent capacitivecoupling between adjacent metal interconnects, low dielectric constant(low k) insulating materials (e.g. dielectric constants less than about4.0) are needed.

Copper interconnect system are typically fabricated using a damasceneprocess in which trenches and vias are etched into dielectric layers.The trenches and vias are filled with copper, which is then planarizedusing, for example, a chemical-mechanical planarization (CMP) process.However, several disadvantages associated with copper damascenestructure have become highlighted as feature sizes continue to decrease.For example, small feature size of the metal lines generally requireshigher aspect ratios, which adversely increases the difficulty infilling such features to form void free metal structures. Forming abarrier layer within high aspect features is particularly difficult.Furthermore, as feature sizes continue to decrease, the barrier layercannot scale, thus resulting in the barrier layer becoming a greaterfraction of that particular feature. Additionally, as the featuredimensions become comparable to the bulk mean free path, the effectiveresistivity of copper features will increase because of non-negligibleelectron scattering at the copper-barrier interface and at grainboundaries.

Accordingly, an alternate metal patterning using subtractive metaletching process has recently gained wide attention. A dry plasma etchingprocess is performed to pattern the metal materials to form one or morepatterns in the interconnect structure. However, current dry plasmaetching processes are primarily performed by physical sputtering whichresults in low selectivity between the metal layer and the hardmasklayer utilized during the etching process. Furthermore, by-productsgenerated during the dry plasma etching process are redeposited on thesidewalls, resulting in tapered profiles and line width increase.

Thus, there is a need for improved methods for patterning a metal line,especially a copper layer, in an interconnection structure with improvedprocess control to form accurate and desired interconnection structuresfor semiconductor devices.

SUMMARY

Embodiments of the present disclosure provide methods for patterning ametal layer, such as a copper layer, to form an interconnectionstructure in semiconductor devices. In one embodiment, a method ofpatterning a metal layer on a substrate includes supplying a firstetching gas mixture comprising a hydro-carbon gas and a hydrogencontaining gas into a processing chamber having a substrate disposedtherein, the substrate having a metal layer disposed thereon, supplyinga second gas mixture comprising the hydrogen containing gas to a surfaceof the etched metal layer disposed on the substrate, and supplying athird gas mixture comprising an inert gas into the processing chamber tosputter clean the surface of the etched metal layer.

In another embodiment, a method of patterning a metal layer on asubstrate includes performing an etching process using a hydro-carbonplasma to etch a metal layer disposed on a substrate in a processingchamber, performing an ashing process using a hydrogen plasma on themetal layer, and performing a sputter cleaning process using an inertgas on the metal layer.

In yet another embodiment, a method of patterning a metal layer on asubstrate includes supplying an etching gas mixture including methane(CH₄) and hydrogen gas to a processing chamber having a substratedisposed therein, the substrate having a metal layer disposed thereon,etching a portion of the metal layer from the substrate, exposing themetal layer to an ashing gas mixture comprising the hydrogen gas to thesubstrate, removing etching byproducts from the substrate, cyclicallysupplying the etching gas mixture and the ashing gas mixture to theprocessing chamber until desired features are formed in the metal layer,and supplying a sputter cleaning gas mixture including a He gas tosputter etch residuals from on the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 depicts an apparatus utilized to pattern a metal layer formed ona substrate to manufacture an interconnection structure;

FIG. 2 depicts a flow diagram of a method for patterning a metal layerto form features into the metal layer to manufacture an interconnectionstructure;

FIG. 3A-3D depict one embodiment of a sequence for patterning a metallayer to form features into the metal layer to manufacture aninterconnection structure depicted in FIG. 2.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

It is to be noted, however, that the appended drawings illustrate onlyexemplary embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

DETAILED DESCRIPTION

Methods for patterning a metal layer on a substrate to form features ina metal layer for interconnection structure manufacturing ofsemiconductor devices are disclosed herein. In one example, thepatterning process is a dry etching process that utilizes a cyclicetching process to incrementally etch the metal layer as well asremoving etching by-products generated during the etching process. Inone example, the etching process is a cyclic etching process thatutilizes a three-stage etching process to etch the metal layer as wellas removing etching by-products generated during the etching process.The three-stage etching process includes a first stage of a main etchingprocess to etch a portion of the metal layer. Subsequently, a secondstage that includes a flash cleaning process is performed to removeetching by-product or surface residuals, thus partially cleaning out thesurface of the etching by-product for further etching. Finally, a thirdstage that includes an energy-driven clean process is then performed toclean remaining by-product on sidewalls or bottom of a feature formed onthe substrate with a higher energy application. By repeatedly performingthe three-stage metal layer patterning process, an accurate control ofetching selectivity and etching stop point may be obtained to provide agood profile control of the features formed in the metal layer. Theetching process may be utilized to form features, trenches, or vias in ametal for an interconnection structure of semiconductor devices.

FIG. 1 is a simplified cutaway view for an exemplary etch processingchamber 100. The exemplary etch processing chamber 100 is suitable forremoving one or more film layers, such as a metal layer, from asubstrate 301. One example of the process chamber that may be adapted tobenefit from the disclosure is an AdvantEdge Mesa Etch processingchamber, available from Applied Materials, Inc., located in Santa Clara,Calif. It is contemplated that other process chambers, including thosefrom other manufactures, may be adapted to practice embodiments of thedisclosure.

The etching processing chamber 100 includes a chamber body 105 having achamber volume 101 defined therein. The chamber body 105 has sidewalls112 and a bottom 118 which are coupled to ground 126. The sidewalls 112have a liner 115 to protect the sidewalls 112 and extend the timebetween maintenance cycles of the etching processing chamber 100. Thedimensions of the chamber body 105 and related components of the etchingprocessing chamber 100 are not limited and generally are proportionallylarger than the size of the substrate 301 to be processed therein.Examples of substrate sizes include 200 mm diameter, 250 mm diameter,300 mm diameter and 450 mm diameter, among others.

The chamber body 105 supports a chamber lid assembly 110 to enclose thechamber volume 101. The chamber body 105 may be fabricated from aluminumor other suitable materials. A substrate access port 113 is formedthrough the sidewall 112 of the chamber body 105, facilitating thetransfer of the substrate 301 into and out of the etching processingchamber 100. The access port 113 may be coupled to a transfer chamberand/or other chambers of a substrate processing system (not shown).

A pumping port 145 is formed through the sidewall 112 of the chamberbody 105 and connected to the chamber volume 101. A pumping device (notshown) is coupled through the pumping port 145 to the chamber volume 101to evacuate and control the pressure therein. The pumping device mayinclude one or more pumps and throttle valves.

A gas panel 160 is coupled by a gas line 167 to the chamber body 105 tosupply process and other gases into the chamber volume 101. The gaspanel 160 may include one or more process gas sources 161, 162, 163, 164and may additionally include inert gases, non-reactive gases, andreactive gases, if desired. Examples of process gases that may beprovided by the gas panel 160 include, but are not limited to,hydrocarbon containing gas such as methane (CH₄), sulfur hexafluoride(SF₆), carbon tetrafluoride (CF₄), hydrogen bromide (HBr), argon gas(Ar), chlorine (Cl₂), nitrogen (N2), helium (He) and oxygen gas (O₂).Additionally, process gases may include chlorine, fluorine, oxygen andhydrogen containing gases such as BCl₃, C₂F₄, C₄F₈, C₄F₆, CHF₃, CH₂F₂,CH₃F, NF₃, CO₂, SO₂, CO, and H₂ among others.

Valves 166 control the flow of the process gases from the sources 161,162, 163, 164 from the gas panel 160. The valves 166, and consequentlythe flow, and are managed by a controller 165. The flow of the gasessupplied to the chamber body 105 from the gas panel 160 may include oneor more of the gases described above.

The lid assembly 110 may include a nozzle 114. The nozzle 114 has one ormore ports for introducing the process gases from the sources 161, 162,164, 163 of the gas panel 160 into the chamber volume 101. After theprocess gases are introduced into the etch processing chamber 100, thegases are energized to form a plasma. An antenna 148, such as one ormore inductor coils, may be provided adjacent to the etching processingchamber 100. An antenna power supply 142 may power the antenna 148through a match circuit 141 to inductively couple energy, such as RFenergy, to the process gas to maintain a plasma formed from the processgas in the chamber volume 101 of the etch processing chamber 100.Alternatively, or in addition to the antenna power supply 142, processelectrodes below the substrate 301 and/or above the substrate 301 may beused to capacitively couple RF power to the process gases to maintainthe plasma within the chamber volume 101. The operation of the powersupply 142 may be controlled by a controller, such as controller 165,that also controls the operation of other components in the etchingprocessing chamber 100.

A substrate support pedestal 135 is disposed in the chamber volume 101to support the substrate 301 during processing. The support pedestal 135may include an electrostatic chuck 122 for holding the substrate 301during processing. The electrostatic chuck (ESC) 122 uses theelectrostatic attraction to hold the substrate 301 to the substratesupport pedestal 135. The ESC 122 is powered by an RF power supply 125integrated with a match circuit 124. The ESC 122 comprises an electrode121 embedded within a dielectric body. The electrode 121 is coupled tothe RF power supply 125 and provides a bias which attracts plasma ions,formed by the process gases in the chamber volume 101, to the ESC 122and substrate 301 positioned thereon. The RF power supply 125 may cycleon and off, or pulse, during processing of the substrate 301. The ESC122 has an isolator 128 for the purpose of making the sidewall of theESC 122 less attractive to the plasma to prolong the maintenance lifecycle of the ESC 122. Additionally, the substrate support pedestal 135may have a cathode liner 136 to protect the sidewalls of the substratesupport pedestal 135 from the plasma gases and to extend the timebetween maintenance of the etch processing chamber 100.

Furthermore, the electrode 121 is coupled to a power source 150. Thepower source 150 provides a chucking voltage of about 200 volts to about2000 volts to the electrode 121. The power source 150 may also include asystem controller for controlling the operation of the electrode 121 bydirecting a DC current to the electrode 121 for chucking and de-chuckingthe substrate 301.

The ESC 122 may include heaters disposed therein and connected to apower source (not shown), for heating the substrate, while a coolingbase 129 supporting the ESC 122 may include conduits for circulating aheat transfer fluid to maintain a temperature of the ESC 122 andsubstrate 301 disposed thereon. The ESC 122 is configured to perform inthe temperature range required by the thermal budget of the device beingfabricated on the substrate 301. For example, the ESC 122 may beconfigured to maintain the substrate 301 at a temperature of about minusabout 25 degrees Celsius to about 500 degrees Celsius for certainembodiments.

The cooling base 129 is provided to assist in controlling thetemperature of the substrate 301. To mitigate process drift and time,the temperature of the substrate 301 may be maintained substantiallyconstant by the cooling base 129 throughout the time the substrate 301is in the etch chamber. In one embodiment, the temperature of thesubstrate 301 is maintained throughout subsequent etch processes atabout 70 to 90 degrees Celsius.

A cover ring 130 is disposed on the ESC 122 and along the periphery ofthe substrate support pedestal 135. The cover ring 130 is configured toconfine etching gases to a desired portion of the exposed top surface ofthe substrate 301, while shielding the top surface of the substratesupport pedestal 135 from the plasma environment inside the etchprocessing chamber 100. Lift pins (not shown) are selectively movedthrough the substrate support pedestal 135 to lift the substrate 301above the substrate support pedestal 135 to facilitate access to thesubstrate 301 by a transfer robot (not shown) or other suitable transfermechanism.

The controller 165 may be utilized to control the process sequence,regulating the gas flows from the gas panel 160 into the etch processingchamber 100 and other process parameters. Software routines, whenexecuted by the CPU, transform the CPU into a specific purpose computer(controller) that controls the etch processing chamber 100 such that theprocesses are performed in accordance with the present disclosure. Thesoftware routines may also be stored and/or executed by a secondcontroller (not shown) that is collocated with the etch processingchamber 100.

The substrate 301 has various film layers disposed thereon which mayinclude at least one barrier layer and a metal layer disposed on thebarrier layer. The various film layers may require etch recipes whichare unique for the different compositions of the other film layersdisposed on the substrate 301. Multilevel interconnects that lie at theheart of the VLSI and ULSI technology may require the fabrication ofhigh aspect ratio features, such as vias and other interconnects.Constructing the multilevel interconnects may require one or more etchrecipes to form patterns in the various film layers. These recipes maybe performed in a single etch processing chamber or across several etchprocessing chambers. Each etch processing chamber may be configured toetch with one or more of the etch recipes. In one example, the etchingprocessing chamber 100 is configured to etch at least a barrier layerdisposed between metal layers to form an interconnection structure. Forthe processing parameters provided herein, the etch processing chamber100 is configured to process a 300 mm diameter substrate, i.e., asubstrate having a plan area of about 0.0707 m², or a 450 mm diametersubstrate. The process parameters, such as flow and power, may generallybe scaled proportionally with the change in the chamber volume orsubstrate plan area.

FIG. 2 is a flow diagram of one example of a method 200 for etching ametal layer, such as a copper layer, for manufacturing aninterconnection structure of a semiconductor device. The etching method200 may be performed in a processing chamber, such as the processingchamber 100 depicted in FIG. 1. FIGS. 3A-3D are schematiccross-sectional view illustrating a sequence for etching a metal layerdisposed on a substrate according to the method 200. Although the method200 is described below with reference to a substrate having a metallayer utilized to form an interconnection structure, the method 200 mayalso be used to advantage transistor device or other manufacturingapplications.

The method 200 begins at block 202 by transferring a substrate, such asthe substrate 301, into a processing chamber, such as the processingchamber 100 in FIG. 1. The substrate 301 may be a silicon based materialor any suitable insulating materials or conductive materials as needed,having a metal layer 304 disposed on the substrate 301 that may beutilized to form an interconnection structure 302 in the metal layer304, as shown in FIG. 3A.

As shown in the exemplary embodiment depicted in FIG. 3A, the substrate301 may have a substantially planar surface, an uneven surface, or asubstantially planar surface having a structure formed thereon. In oneembodiment, the substrate 301 may be a material such as crystallinesilicon (e.g., Si<100> or Si<111>), silicon oxide, strained silicon,silicon germanium, doped or undoped polysilicon, doped or undopedsilicon wafers and patterned or non-patterned wafers silicon oninsulator (SOI), carbon doped silicon oxides, silicon nitride, dopedsilicon, germanium, gallium arsenide, glass, sapphire. In the examplewherein a SOI structure is utilized for the substrate 301, the substrate301 may include a buried dielectric layer disposed on a siliconcrystalline substrate. In the example depicted herein, the substrate 301may be a crystalline silicon substrate.

In one particular embodiment, the substrate 301 may have a barrier layer351 disposed between the metal layer 304 and a low-k insulatingdielectric material 350, as shown in dotted line in FIG. 3A. It is notedthat the barrier layer 351 and the low-k insulating material 350 areeliminated in the embodiments depicted in FIGS. 3B-3D for brevity andease of explanation. The barrier layer 351 may be fabricated from TaN,TiN, AlN, TaSiN, TiSiN, or other suitable materials. Suitable examplesof the low-k insulating dielectric material 351 includes SiO containingmaterials, SiN containing materials, SiOC containing materials, SiCcontaining materials, carbon based materials, or any other suitablematerials.

In one embodiment, the metal layer 304 is disposed on the substrate 301.The metal layer 304 may be fabricated from tungsten (W), tantalum (Ta),titanium (Ti), copper (Cu), ruthenium (Ru), nickel (Ni), cobalt (Co),chromium (Cr), iron (Fe), manganese (Mn), aluminum (Al), hafnium (Hf),vanadium (V), molybdenum (Mo), palladium (Pd), gold (Au), silver (Au),platinum (Pt), alloys thereof, and combinations thereof, among others.In the example depicted in FIGS. 3A-3D, the metal layer 304 is a copperlayer or a copper alloy layer having a thickness between about 200 Å andabout 500 Å, such as about 350 Å.

A patterned mask layer 306, a lithographically patterned mask or ahardmask layer, is then formed over the metal layer 304, exposingportions 310 of the metal layer 304 for etching. In one embodiment, thepatterned mask layer 306 may is a positive tone photoresist, a negativetone photoresist, a UV lithography photoresist, an i-line photoresist,an e-beam resist (for example, a chemically amplified resist (CAR)) orother suitable photoresist. In one example, the patterned mask layer 306may include organic polymer materials, such as fluoropolymers,silicon-containing polymers, hydroxy styrene, or acrylic acid monomersto provide acid groups when the mask layer 306 is exposed to radiation.

In another embodiment, the patterned mask layer 306 is a hardmask layerfabricated by a dielectric layer. The patterned mask layer 306 may be asingle layer of dielectric material, composite layers of dielectricmaterials, or a film stack with different types of material includingmetal containing layer, dielectric materials and organic materials.Suitable examples of the patterned mask layer 306 include silicon oxide,silicon oxynitride, silicon carbide, amorphous carbon, siliconcarbon-nitride (SiCN), TaN, Ta, TiN, or Ti and the like. In oneembodiment, the patterned mask layer 306 is a layer of TaN, Ta, Ti orTiN.

At block 204, a first etching gas mixture is supplied into theprocessing chamber 100 to etch the portions 310 of the metal layer 304exposed by the patterned mask layer 306, as shown in FIG. 3B, until apredetermined first depth 314 of a feature 320 is formed in the metallayer 304. The patterned mask layer 306 serves as an etching mask duringthe etching process of the metal layer 304. The etching gas mixture iscontinuously supplied to etch the metal layer 304 until the depth 314 ofthe feature 320 are formed in the metal layer 304. In one embodiment,the depth 314 may be between about 3 Å and about 100 Å, such as about 5Å and about 30 Å. Alternately, the depth 314 may be between about 5percent and about 15 percent of the thickness of the metal layer 304.

During the etching process, etching by-product 316 may be adverselyaccumulated or adhered on surfaces of the patterned mask layer 306.Accordingly periodic cleaning process, which will be described later atblock 206 and 208, is necessary to maintain cleanness of the substratesurface to continue etching the metal layer 304 with desired andaccurate profile transfer and control.

In one embodiment, the etching gas mixture selected to etch the metallayer 304 includes at least a hydrocarbon containing gas having aformula C_(x)H_(y), wherein x and y are integers ranging from 1 to 8 and4 to 18 respectively. Suitable examples of the hydrocarbon containinggas include methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane(C₄H₁₀), pentane (C₅H₁₂), hexane (C₆H₁₄), propene, ethylene, propylene,butylene, pentene, combinations thereof and the like. In a particularexample, the hydrocarbon containing gas is methane (CH₄).

It is believed that a hydrocarbon containing gas may efficiently reactwith the metal layer, such as copper atoms, forming by-products. Forexample when the metal layer 304 includes copper, an etch by-product316, such as a hydro-carbon-copper complex, such as CH_(x)Cu_(y)H_(z)like compounds (x, y, z are integers) including CH₃Cu, CHCu, CH₂Cuand/or other related compounds, may be formed in gas phase or in a solidmatrix which can be later removed from the surface of the substrate 301.Copper surface atoms exposed to CH₄ plasma are excited into high energystate due to the energetic ions, electrons, and photon bombardment fromthe CH₄ plasma, and form the by-product 316, such as thehydro-carbon-copper complex, such as CH_(x)Cu_(y)H_(z) like compounds(x, y, z are integers) including CH₃Cu, CHCu, CH₂Cu and/or other relatedcompounds. The complex 316 may be in a gas phase readily pumps out ofthe processing chamber. The complex 316 may be in solid matrix whichreadily falls on the substrate surface or feature sidewalls.

While supplying the etching gas mixture, an inert gas may also besupplied with the etching gas mixture to assist the profile control asneeded. Examples of the inert gas supplied in the gas mixture includeAr, He, Ne, Kr, Xe or the like.

In one example, a hydrogen containing gas may be supplied in the firstetching gas mixture with the hydrocarbon containing gas. Suitableexamples of the hydrogen containing gas include H₂, H₂O, H₂O₂, NH₃, andthe like. It is believed that the hydrogen gas supplied in the first gasmixture may assist reacting with the copper elements from the metallayer, forming carbon-copper complex which may be later removed from thesubstrate surface during a cleaning process. In one example, thehydrogen containing gas is H₂ gas.

In one example, the hydrocarbon gas supplied in the first etching gasmixture may be maintained at a flow rate by volume between about 5 sccmand about 100 sccm. The optional inert gas may be supplied to theprocessing chamber at a flow rate by volume between about 30 sccm andabout 100 sccm. The hydrogen containing gas may be supplied in the firstetching gas mixture us between about 1 sccm and about 100 sccm, such asabout 50 sccm. In one embodiment, the hydrocarbon gas and the hydrogencontaining gas may be supplied in the first etching gas mixture at aratio (by volume) of between about 5:1 and about 1:5, such as about 1:1.

After the etching gas mixture is supplied to the processing chambermixture, RF source power is supplied to form a plasma from the etchinggas mixture therein. The RF source power may be supplied between about500 Watts and about 2000 Watts and at a frequency between about 400 kHzand about 13.56 MHz. A RF bias power may also be supplied as needed. TheRF bias power may be supplied between 100 Watts and 1500 Watts, such asbetween about 750 Watts. In one embodiment, the RF source power may bepulsed with a duty cycle between about 10 to about 95 percent at a RFfrequency between about 500 hz and about 10 kHz.

Several process parameters may also be controlled while supplying theetching gas mixture to perform the etching process. The pressure withinthe processing chamber may be controlled at between about 0.5 milliTorrand about 500 milliTorr, such as between about 2 milliTorr and about 30milliTorr. A substrate temperature is maintained between about 15degrees Celsius to about 300 degrees Celsius, such as greater than 50degrees Celsius, for example between about 60 degrees Celsius and about150 degrees Celsius, like 90 degrees Celsius. It is believed that hightemperature, temperature greater than 50 degrees Celsius, helps reducethe amount of etching byproduct deposition on the substrate. The etchingprocess may be performed for a duration of between about 10 seconds andabout 30 seconds, such as about 15 seconds, to etch the metal layer 304with the depth 314 for between about 30 Å and about 100 Å.Alternatively, the etching process may remove between about 10 percentand about 30 percent of the thickness of the metal layer 304 from thesubstrate 301.

At block 206, an ashing process may be performed to remove etchingby-products 316 and/or other related compounds from the substrate, asshown in FIG. 3C. During etching of the metal layer 304 at block 204,by-products 316, hydro-carbon-copper complex 316, such asCH_(x)Cu_(y)H_(z) like compounds (x, y, z are integers) including CH₃Cu,CHCu, CH₂Cu and/or other related compounds, which are not formed in agas phase that can be readily pumped out from the processing chamber,may become solid precipitate falling on the substrate surface. As theby-products 316 and/or other related compounds accumulates, the features320 being formed in the metal layer 304 may be deformed and distorted.Accordingly, an ashing process may be performed to efficiently andtimely remove the by-products 316 and/or other related compounds fromthe substrate surface.

In one example, the ash process may be performed by supplying a secondgas mixture, such as an ash gas mixture, into the processing chamber.The ash process may be an isotropic etching process to remove theby-products 316 and/or other related compounds from the substrate 301.

In one example, the second gas mixture including at least one hydrogencontaining gas and optionally an inert gas into the processing chamberto react with the by-products and/or other related compounds 316 fromthe substrate 301. The hydrogen containing gas and/or an inert gassupplied from the second gas mixture forms carbon hydrogen gas or othercarbon containing byproducts with the by-products 316 and/or otherrelated compounds in gas phase to be pumped out of the chamber. In oneexample, the hydrogen containing gas supplied in the ash gas mixtureincludes H₂ and the inert gas supplied in the ash gas mixture includesHe, Ar, and the like.

During the ash process, several process parameters may be regulated tocontrol the ash process. In one example, a process pressure in thevacuum processing chamber 100 is regulated between about 4 mTorr toabout 50 mTorr, for example, at about 30 mTorr. A RF source power may beapplied to 500 Watts to about 2000 Watts to maintain a plasma inside thevacuum processing chamber 100. Additional, a relatively low RF biaspower less than 200 Watts, such as less than 100 Watts, for examplebetween about 10 Watts and about 50 Watts, may be utilized during theashing process. The second gas mixture may be flowed into the processingchamber at a rate of between about 100 sccm to about 300 sccm, such asabout 200 sccm. The ashing process may be performed for a duration ofbetween about 10 seconds and about 120 seconds, such as about 15seconds. A substrate is maintained at a temperature of between about 15degrees Celsius to about 300 degrees Celsius, such as greater than 50degrees Celsius, for example between about 60 degrees Celsius and about110 degrees Celsius, such as about 90 degrees Celsius. It is believedthat high temperature, temperature greater than 50 degrees Celsius,helps reduce the amount of etching byproduct deposition on thesubstrate.

After the ashing process is performed, the by-products 316 and/or otherrelated compounds present on the substrate 301 are substantially removedfrom the substrate 301. After the by-products 316 and/or other relatedcompounds is removed from the substrate 301, a second cycle of theetching process at block 204 and the ashing process 206 may be performedto resume the etching process, as indicated by the loop 212.

In some embodiments, the process at block 204 and 206 may be repeatedlyperformed, as indicated by the loop 212, to etch and clean the substrate310 until a desired depth of features is formed in the metal layer 304.In one embodiment wherein the etching by-product 316 may not beefficiently cleaned during the process at block 206, an additionalgentle sputtering cleaning process may be performed, which will bedescribed in greater detail at block 208, to assist cleaningresiduals/by-products on a bottom, sidewalls, or surface of the features320 formed in the metal layer 304.

In one embodiment, the process at block 204 and at block 206 may beperformed repeatedly for about 7 and about 10 times. Each cycle of theprocess may remove about 10 Å and about 50 Å from the thickness of themetal layer 304.

At block 208, after the cleaning process performed at block 206, atreating process, such as a sputter cleaning process, may be performedto gently sputter the surface of the substrate 301, so as to removeetching by-products 316 or residuals from the substrate 301. The sputtercleaning process provides a gentle surface sputtering effect to removeand sputter the etching by-products or residuals formed in the areaswhich may not be easily removed by conventional pump-purge process, suchas in the areas of sidewalls or bottoms of the features 320 formed inthe metal layer 304. After the sputter clean process, the surfaces(e.g., bottom or sidewalls) of the features may then be exposed again,providing fresh surface to be readily etched again until a desiredprofile is formed in the metal layer 304. Furthermore, as discussedabove, the etching by-products/residuals may be certain types of thepolymer by-products generated at block 204, which may be adhered orstuck on the substrate 301, and which may not be easily removed by achemical process. As such, a gentle physical sputtering process asperformed at block 208 may assist physically bombard and sputter off thepolymer by-products from the substrate surface without aggressivelydamaging the structures formed on the substrate 301.

In one example, the sputter cleaning process is performed by supplying athird gas mixture to the processing chamber that includes at least aninert gas. The inert gas supplied from the third gas mixture may gentlysputter clean the etching by-products 316 or residuals remaining on thesubstrate so as to provide a clean surface to etch the metal layer 304with good profile/feature transfer. In one example, the inert gassupplied in the third gas mixture includes one or more of He, Ar, andthe like. In one particular example, the third gas mixture includes a Hegas.

In one example, the H₂ gas supplied in the third etching gas mixture maybe maintained at a flow rate by volume of between about 5 sccm and about500 sccm, such as about 10 sccm and about 150 sccm. The He gas suppliedin the third etching gas mixture may be maintained at a flow rate byvolume between about 5 sccm and about 500 sccm, such as about 10 sccmand about 150 sccm. In one example, the H₂ gas and the He gas suppliedin the third etching gas mixture may be controlled at a ratio betweenabout 1:3 and about 3:1, such as about 1:1.

After the third etching gas mixture is supplied to the processingchamber mixture, RF source power is supplied to form a plasma from thethird etching gas mixture therein. The RF source power may be suppliedbetween about 100 Watts and about 2000 Watts and at a frequency betweenabout 400 kHz and about 13.56 MHz. A RF bias power may also be suppliedas needed. The RF bias power may be supplied at less than 300 Watts,between about 30 Watts and about 250 Watts, to maintain minimum biasbombardment impact to the substrate. In one embodiment, the RF sourcepower may be pulsed with a duty cycle between about 10 to about 95percent at a RF frequency between about 500 Hz and about 10 kHz.

Several process parameters may also be controlled while supplying theetching gas mixture to perform the treatment process. The pressure ofthe processing chamber may be controlled at between about 0.5 milliTorrand about 500 milliTorr, such as between about 4 milliTorr and about 30milliTorr. A temperature is maintained at a temperature between about 15degrees Celsius to about 300 degrees Celsius, between about 5 degreesCelsius and about 100 degrees Celsius, for example about 90 degreeCelsius. The third etching gas may be provided for between about 10seconds and about 150 seconds, such as about 75 seconds, to deep cleanthe surface of the substrate 301.

Similarly, the processes at blocks 204, 206 and 208 may be repeatedlyperformed, as indicated by the loop 210, to etch and clean the substrate310 until a desired depth of features 322 is formed in the metal layer304, as shown in FIG. 3D. In one example wherein the etching by-product316 may not be efficiently cleaned during the process described at block206, the additional gentle sputtering cleaning process at block 208 maybe performed, as indicated by the loop 210, to assist cleaningaccumulated or sticky polymer residuals/by-products on a bottom,sidewalls, or surface of the features 322 formed in the metal layer 304.

The processes at blocks 204, 206 and 208 may be repeatedly performeduntil the feature 322 is formed in the metal layer 304, exposingportions 324 of the substrate 301, as shown in FIG. 3D, so that theprocess 200 may then be terminated and completed. It is noted that theprocesses of blocks 204 and 206 and 208 may be repeatedly performed asmany times or in any number as needed until the metal layer 304 exposedby the patterned mask layer 306 is etched, forming the desired feature322.

In one particular example, the processes at blocks 204 and 206 may beperformed 7 times to 10 times, the process at block 208 may be thenperformed. In addition, if some extra cleaning are desired to be done,e.g., residual remaining present on the substrate, a final round of theprocess at block 204, 206 and 208 may be performed. In this final round,the process at block 208 may be performed for a long time to ensure thedesired degree of cleanness on the substrate surface is achieved. Inthis example, the final round of the process for performing the processat block 208 may be controlled for a period of time of between about 200seconds and about 400 seconds, such as about 300 seconds, as needed.

At block 214, the desired feature profile and/or the structure 322 ofmetal layer 304 is formed on the substrate 301. After the desiredfeature profile and/or the structure 322 of metal layer 304 is formed onthe substrate 301, the part of the patterned mask layer 306 may beremoved, leaving a portion of the mask layer 306 on the patterned metallayer 304.

In the example depicted in FIG. 3D, most of the patterned mask layer 306is consumed during the etching process and only leaving a predeterminedthickness of the patterned mask layer 306 remaining on the substrate forthe subsequent interconnection process. In some cases, the patternedmask layer 306 is removed from the substrate after the metal layeretching process is completed.

Thus, methods for etching a metal layer to form interconnectionstructure are provided. The etching process utilizes cyclic etching andashing process and sputter cleaning process to etch features in a metallayer with good feature/profile control. The methods may advantageouslyprovide the etching process with good metal feature control and etchingefficiency, thereby improving feature formation with desired dimensionand profile formed in the metal layer disposed on a substrate inapplications for interconnection structures of semiconductor chips.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method of patterning a metal layer on asubstrate, comprising: (a) supplying a first etching gas mixturecomprising a hydro-carbon gas and a hydrogen gas (H₂) into a processingchamber having a substrate disposed therein, the substrate having ametal layer disposed thereon; (b) supplying a second gas mixturecomprising the hydrogen containing gas to a surface of the etched metallayer disposed on the substrate; and (c) supplying a third gas mixturecomprising Ar gas or He gas into the processing chamber to sputter cleanthe surface of the etched metal layer.
 2. The method of claim 1, furthercomprising: performing (a) and (b) repeatedly until desired features areformed in the metal layer.
 3. The method of claim 1, further comprising:performing from (a) to (c) repeatedly until desired features are formedin the metal layer.
 4. The method of claim 3, wherein after performingin a final cycle of processes (a) and (b), the process of step (c) isperformed at a period of time longer than that in which (a), (b) and (c)were performed.
 5. The method of claim 1, the metal layer is a copperlayer.
 6. The method of claim 1, wherein supplying the first gas mixturefurther comprises: etching the metal layer to a depth of between about 5Å and about 30 Å.
 7. The method of claim 1, wherein performing (a) and(b) further comprises: performing (a) and (b) repeatedly between about 7and 10 times.
 8. The method of claim 1, wherein the hydro-carbon gas isselected from a group consisting of methane (CH₄), ethane (C₂H₆),propane (C₃H₈), butane (C₄H₁₀), pentane (C₅H₁₂), hexane (C₆H₁₄),propene, ethylene, propylene, butylene, pentene and combinationsthereof.
 9. The method of claim 1, wherein the hydro-carbon gas ismethane (CH₄).
 10. The method of claim 1, wherein He gas is supplied inthe third gas mixture.
 11. The method of claim 1, wherein supplying thesecond gas mixture further comprises: removing etching byproducts fromthe substrate surface.
 12. The method of claim 1, wherein supplying thethird gas mixture further comprising: sputtering etching byproducts fromthe substrate surface.
 13. The method of claim 11, wherein the etchingbyproduct includes hydro-carbon-copper complex compound.
 14. The methodof claim 1, wherein the substrate temperature is controlled at greaterthan 50 degrees Celsius during (a).
 15. A method of patterning a metallayer on a substrate, comprising: (a) performing an etching processusing a hydro-carbon plasma to etch a metal layer disposed on asubstrate in a processing chamber; (b) performing an ashing processusing a hydrogen plasma on the metal layer; (c) performing a sputtercleaning process using Ar gas or He gas on the metal layer; andperforming (a) and (b) repeatedly or (a) to (c) repeatedly until desiredfeatures are formed in the metal layer.
 16. The method of claim 15,wherein the etching process removes between about 5 percent and about 15percent of a thickness of the metal layer from the substrate.
 17. Amethod of patterning a metal layer on a substrate, comprising: supplyingan etching gas mixture including methane (CH₄) and hydrogen (H₂) gas toa processing chamber having a substrate disposed therein, the substratehaving a metal layer disposed thereon; etching a portion of the metallayer from the substrate; exposing the metal layer to an ashing gasmixture comprising the hydrogen gas to the substrate; removing etchingbyproducts from the substrate; cyclically supplying the etching gasmixture and the ashing gas mixture to the processing chamber untildesired features are formed in the metal layer; and supplying a sputtercleaning gas mixture including a He gas to sputter etch residuals fromthe substrate.